Switch construction with load break device having a movable slat, a gas expansion chamber and a gas muffler

ABSTRACT

Switch construction for power distribution alternating current circuits having a switch blade for pivotal movement into and out of contacts enclosed by an insulating housing having a slot through which the switch blade is movable. A slat is biased transversely of the slot to close off the space between the switch blade and the contacts on opening of the circuit. A gas expansion chamber at the entrance to the slat is closed off by a pair of flexible insulating strips. A gas muffler is located at one end of the expansion chamber. The switch blade, in closed position, is spaced from the housing, the slat and the sealing strips by heat resisting spacers.

[451 June 20, 1972 United States Patent Harner et al.

France...............................200/151 R S m N m m m T m A m w m n m P m A m m R m c m 0 m m a s a T m S mu m c n k T o m A 0 l P 98 R 7 N 53 w G WW a 4 R IN m 0 m W F Wm B m 6 46 i m m M 3 1 P Meister, Evanston, both of 111.

AttorneyRoben R. Lockwood [73] Assignee:

[22] Filed:

S & C Electric Company, Chicago, 111.

Jan. 7, 1971 ABSTRACT Switch construction for power distribution alternatin g current 2 l] Appl. No.: 104,589

circuits having a switch blade for pivotal movement into and out of contacts enclosed by an insulating housing having a slot through which the switch blade is movable. A slat is biased transversely of the slot to close off the [52] [1.8. R, 200/146 R, 200/15] R .........H0ln 33/08 space between the [58] Field of Search..................................200/l46, 151, 144 switch blade and the contacts on Opening of the circuit A gas slat is closed off by a gas muffler is located at one expansion chamber at the entrance to the pair of flexible insulating strips. A

[56] References Cited UNlTED STATES PATENTS end of the expansion chamber. The switch blade, in closed position, is spaced from the housin strips by heat resisting spacers.

g, the slat and the sealing 200/148 C ,...200/ 148 C 200/148 C l 1 Claims, 19 Drawing Figures PATENTEuJuuzo m2 3,671,697

sum 301- 4 SWITCH CONSTRUCTION WITH LOAD BREAK DEVICE HAVING A MOVABLE SLAT, A GAS EXPANSION CHAMBER AND A GAS MUFFLER This invention is an improvement over the invention disclosed in Jeffries application Ser. No. 813,541, filed Apr. 4, 1969 now U.S. Pat. No. 3,576,967, issued May 4, 1971.

In the above application a switch construction is disclosed in which a switch blade is mounted for pivotal movement with respect to contacts enclosed in an insulating housing having a slot through which the switch blade is pivoted. A pair of slats mounted in grooves in the housing along one side of the slot are biased toward the other side of the slot to close off the space between the switch blade and the contacts when the switch blade is in the open position. This arrangement has been successful in limiting flow of gas and are products toward the switch blade which otherwise tended to cause flashover across the gap between the switch blade and the contacts and consequent failure to clear or open the circuit. When this type of switch construction is employed in certain types of metal enclosures, it is necessary to reduce to a minimum the spacing between adjacent phases of a polyphase switch with the result that the phase to phase and the phase to ground clearances are minimal. Exhaust gas and are product flow patterns then assume relatively great importance and, if not adequately controlled, may result in phase to phase or phase to ground flashovers even though the circuit may be successfully interrupted.

Accordingly, among the objects of this invention are: To prevent substantially all gas and arc product discharge of a harmful nature in the operation of a circuit interrupter that would lead to a phase to phase or phase to ground flashover or would cause flashover between the switch blade and the contacts from which the switch blade is separated; to cool and condense the gas and are products incident to opening an alternating current electric power circuit operating, for example, at a voltage of the order of IS Kv. and in which the current flow may range up to 600 amperes; to seal off the space between the switch blade and the switch contacts when the former is moved to the switch open position in addition to sealing action that is provided by an insulating slat movable transversely of a slot in an insulating housing through which the switch blade pivots; to provide a gas expansion chamber at the entrance of the slot in the insulating housing one side of which is closed by a pair of flexible sealing strips; and to cool, condense, and deionize the gas and arc products in the gas expansion chamber by a muffler located at the end of the gas expansion chamber past which the distal end of the switch blade ivots.

p According to this invention a switch blade is arranged to pivot into and out of engagement with stationary contacts through a slot in an insulating housing enclosing the contacts. A gas expansion chamber is provided along the entrance to the slot with its inner side being closed off by an insulating slat that is biased transversely of the slot and is displaced by the switch blade. The outer side of the gas expansion chamber is closed off by a pair of flexible resilient strips of insulating material between which the switch blade pivots. The gas and arc products incident to the arc drawn on opening of the circuit flow from the gas expansion chamber through a muffler at the end of it past which the distal end of the switch blade swings in moving to the switch open position. The mufiler comprises spaced perforated insulating platesbetween which are product cooling and condensing pellets are positioned which are capable of absorbing the gas and conducting particles incident to circuit interruption and cooling the same so as to permit only a harmless discharge of non-conducting material from the muffler. Heat resisting spacers on the housing, slat and sealing strips space the switch blade therefrom when it is in the switch closed position. They may be omitted for lower ampere rated switches.

In the drawings:

FIG. 1 is a view, in front elevation, of a three phase switch construction in which this invention is embodied.

FIG. 2 is a view in side elevation and taken generally along line 2-2 of FIG. 1 to show one of the phase switch assemblies.

FIG. 3 is a view, in side elevation and at anenlarged scale of one of the insulating housings forming apart of each circuit interrupter. 1

FIG. 4 is a view, in bottom plan, of the insulating housing shown in FIG. 3.

FIG. 5 is a sectional view taken generally along line 5-5 of FIG. 3.

FIG. 6 is a sectional view at an enlarged scale taken generally along line 6--6 of FIG. 3.

FIG. 7 is a sectional view at an enlarged scale taken generally along line 7-7 of FIG. 3.

FIG. 8 is an elevational view of the inside of the left housing plate.

FIG. 9 is an elevational view of the inside of the right housing plate.

FIG. 10 is a plan view of the slat.

FIG. 11 is a view, partly in side elevation and partly in section of the slat-shown in FIG. 10.

FIG. 12 is a vertical sectional view taken generally along line 12-12 of FIG. 10.

FIG. I3 is a plan view of the switch blade shown at an enlarged scale.

FIG. 14' is a view, in side elevation, of the switch blade shown in FIG. 13.

FIG. 15 is a top plan view of the switch blade shown in FIG. 13.

FIG. 16 is a view in side elevation of one of the flexible resilient sealing strips.

FIG. 17 is an end view at an enlarged scale of the sealing strip shown in FIG. 16.

FIG. 18 is a sectional view, at an enlarged scale, showing the sealing strips and the heat resisting spacers thereon.

FIG. 19 is a view, similar to FIG. 18, showing the switch blade in switch closed position between the heat resisting spacers.

In FIGS. 1 and 2 the reference character 10 designates, generally, a three phase switch construction. It includes a metallic frame 11 on which three phase switch assemblies, in dicated generally at 12, 13 and 14, are mounted. Each of the phase switch assemblies comprises a switch blade 15 that is secured to a metallic switch blade support plate I6 that is carried by insulators 17 which are mounted to pivot about -a horizontal axis 18. For this purpose an operating handle 19 can be employed although it will be understood that other operating means can be used for pivoting the switch blade I5 from the switch open position shown by broken lines in FIG. 2

to the switch closed position shown by full lines. Connection to the switch plate support blade 16 is made by a sliding contact 20 which is mounted on and secured to a terminal 21. The terminal 21 is mounted on a lower insulator 22 which is carried by the metallic frame I 1.

Each phase switch assembly also includes a stationary contact assembly that is indicated generally at 25 and is shown in detail by broken lines in FIG. 5. The contact assembly 25 in- .cludes contact buttons 26 that are carried by the distal ends of 1 extinguishing structure in the form of an insulating housing that is indicated, generally, at 33. Its construction is shown in detail in FIGS. 3, 4 and 5. The insulating housing 33 is generally sector shaped, is formed of a suitable plastic material from which an arc extinguishing medium can be evolved and is arranged, as shown particularly in FIG. 5, to enclose the stationary contact assembly 25 except for that portion of the bracket terminal-29 which extends therefrom. The insulating housing 33 is secured by bolts 34 to the bracket terminal 29.

The insulating housing 33 is provided with a slot 35 for receiving the switch blade 15 in its pivotal movement into and out of engagement with the stationary contact assembly 25. The slot 35, as shown in FIGS. 4 and 7, is chamfered at 36 and 37 at the entrance 38 where the switch blade 15 first is swung into the insulating housing 33. This construction accommodates a limited degree of misalignment of the switch blade 15 with respect to the insulating housing 33.

It will be understood that the insulating housing 33 is formed of a left housing plate 40, which is indicated generally by this reference character in FIG. 8. Also the insulating housing 33 is formed by a right housing plate 41 which isindicated generally by this reference character in FIG. 9. Bolts 42 and 43 are employed for securing the left and right housing plates 40 and 41 together to provide a unitary construction. Theleft housing plate 40 has a left housing contact cover section 44 formed integrally therewith for overlying a portion of the stationary contact assembly 25 as seen in FIG. 5. Similarly the right housing plate 41 has an integral right housing contact cover section 45. Extending from these cover sections 44 and 45 are left and right contact covers 46 and 47, FIG. 5, which complete the enclosure for the stationary contact assembly 25 and interpose a barrier between it and the adjacent contact assembly and ground. They are secured by the bolts 34 and one of the bolts 42 to the plates 40 and 41 and to the bracket terminal 29.

For closing off the space between the stationary contact assembly 25 and the switch blade 15 when the latter is in the open position a slat, indicated generally at 48 in FIGS. 10, 11 and 12, is employed. The slat 48 is located in a groove 49 in the right housing plate 41 and is movable into a complementary groove 50 in the left housing plate 40 by coil compression springs one of which is shown at 51 in FIG. 5. Two of the springs 51 are employed and they are positioned in recesses 52 in the right housing plate 41. The springs 51 extend into recesses 53 that are formed in the slat 48. It is understood that the slat 48 is molded of a suitable insulating material from which an arc extinguishing medium is evolved upon impingement thereon by the are that is drawn between the switch blade 15 and the stationary contact assembly 25 during the switch opening operation. As shown in FIGS. and 11, the slat 48 has a chamfered edge 54 for receiving the distal end of the switch blade as it is swung into the switch closed position for displacing the slat 48 from its position shown, for example, in FIG. 5 when the switch assembly is open.

It is desirable that the switch blade 15 be spaced from the housing plate 40 and from the slat 48 when it occupies the switch closed position. The reason for this is that the temperature of the switch blade 15 may be raised to a very high value in the event that short circuit current of the order of many thousands of amperes should flow through it. Accordingly a heat resisting spacer 55 of suitable material is provided in the slat 48 and heat resisting spacers 56 are provided in the left housing plate 40 as shown in FIG. 8. Also as here shown a groove 57 is formed in the bottom of the groove 50 for receiving the heat resisting spacer 55 in the absence of the switch blade 15 in order to more completely close off the space between it and the stationary contact assembly 25.

The construction thus far described is generally the same as that disclosed in the above identified application. While this construction is satisfactory for confining and extinguishing the are that is drawn between the switch blade 15 and the contact assembly 25 there still remains the disposition of the gas and are products which are incident to the drawing of the arc and which are likely under certain circumstances to cause a flashover from one phase to another phase or from a phase to ground. It is to the provision of such undesired flashovers that this invention is particularly directed.

For this purpose there is provided a gas expansion chamber along the entrance 38 to the slot 35 as shown more clearly in FIGS. 5 and 6 of the drawings. The gas expansion chamber is indicated, generally, at 61 and it is formed by grooves 62 and 63 which are provided in the housing plates 40 and 41 along the entrance 38 to the groove 35. As shown in FIG. 7 the slot 35 extends from the gas expansion chamber 31 where the plates 40 and 41 are chamfered as indicated at 64 and 65 to facilitate continued movement of the switch blade 15 toward the stationary contact assembly 25.

It will be understood that the outer side of the gas expansion chamber 61, which is generally rectangular in cross section, is closed along the entrance 38 by flexible resilient sealing strips that are indicated, generally, at 66 and 67. The sealing strips 66 and 67 are formed of a material which retains its elastic properties at extremes of temperature, does not take a permanent set due to mechanical stress, is capable of withstanding the impact incident to pivotal movement of the switch blade 15 and is capable of resisting lubricants that are used on the surfaces of the contact buttons 26. It has been found that materials such as polysulfone and polycarbonate are satisfactory for this purpose.

The construction of the flexible resilient sealing strips 66 and 67 is of importance. As shown particularly in FIGS. 7, 16 and 17, the sealing strips 66 and 67 have integrally formed bulbous sections 68 and 69 that interfit with enlarged sections 70 and 71 of sealing strip receiving slots 72 and 73 which extend in the housing plates 40 and 41 along the entrance 38 to the slot 35. The slots 72 and 73 have relatively narrow openings 74 and 75 through which relatively thin flexible sections 76 and 77 of the sealing strips 66 and 67 extend laterally into the gas expansion chamber 61. The distal edges 78 and 79 of the flexible sections 76 and 77 are juxtaposed as shown more clearly in FIGS. 5 and 7 of the drawings. Heat resisting spacers 80 and 81, FIGS. 18 and 19, are provided on the sealing strips 66 and 67 to space them from the switch blade 15 in the switch closed position. The sealing strips 66 and 67 form an inverted V-shape for receiving the switch blade 15 and for maintaining close contact engagement therewith to seal the outside of the gas expansion chamber 61 particularly when the switch blade 15 is swung toward the switch open position. To facilitate this sealing engagement the edges or sides of the switch blade 15 are contoured or chamfered as indicated at 82 and 83 in FIGS. 13, 14 and 15. Also the upper end 84 is similarly shaped. By positioning the sealing strips 66 and 67 as described and shown in FIG. 7 with the apex of the V-shape facing in the direction of gas flow there is a tendency for the pressure that is generated in the gas expansion chamber 61 to cause the juxtaposed edges 78 and 79 to engage closely the surface of the switch blade 15. The material of the sealing strips 66 and 67 is such that the edges 78 and 79 follow the contour of the switch blade 15 and thereby provide an effective seal along the sides 82 and 83 as well as along the end 84.

Silver strips 85 are inlaid on opposite sides of the switch blade 15 to provide low contact resistance engagement with the contact buttons 26.

As pointed out the outer side of the gas expansion chamber 61 is sealed off by the flexible sealing strips 66 and 67 as the switch blade 15 moves therebetween. The right or lower end of the gas expansion chamber 61 is closed 011' by the adjacent portions of the plates 40 and 41 of the insulating housing 33. The gas and arc products then can escape only through the left or upper end of the gas expansion chamber 61. However it is desirable to cool, condense and deionize them before they are vented to the atmosphere. It is for this purpose that a muffler, indicated generally at 88 in FIGS. 3, 6 and 7, is employed. The muffler 88 comprises an outer plate 89 of suitable plastic insulating material which is provided with exhaust perforations 90. The outer plate 89 has inturned sides 91 which interfit with grooves 92 along the outer edges of the housing plates 40 and 41. If desired these sides 91 can be heat sealed to the plates 40 and 41. The muffler 88 also is formed by an inner plate 95 which is spaced from the outer plate 89 and has perforations 96 to permit the gas and are products to flow therethrough. The sides of the inner plate 95 bear against shoulders 98 and 99 that are formed in the plates 40 and 41 as shown in FIG. 6. Formed integrally with the inner plate 95 is a generally V- Shaped section 100 that is shown more clearly in FIG. 7. The

V-shaped section 100 extends upwardly and outwardly and into juxtaposition with the inside of the outer plate 89 and is provided to receive the outer ends of the flexible sealing strips 66 and 67 which extend therethrough and into abutting engagement with the inside of the outer plate 89.

The space between the outer and inner plates 89 and 95 of the muffler 88 is filled with are product cooling and condensing means which preferably takes the form of pellets or spheres 101 of a material such as activated alumina. This material retains its form under high temperature conditions and is capable of absorbing gases. Preferably the spheres or pellets 101 have a diameter of one-eighth inch and, while providing a relatively large surface area, yet an adequate void space is provided therebetween so that the pressure drop through them is not excessive.

In operation, when the switch blade is pivoted to the switch closed position, its distal end engages the resilient sealing strips 66 and 67 and spreads the edges 78 and 79 apart. The continued pivotal movement of the switch blade 15 extends through the slot 35 with the edges 78 and 79 closely following the surface contour of the switch blade 15. The distal end of the switch blade 15 engages the slat 48 at the chamfered edge 54 and displaces it from the groove 50 in the plate 40 into the groove 49 in the plate 41 and finally it engages and completes the circuit to the stationary contact assembly 25. In this position the heat resisting spacers 55 and 56 hold the switch blade 15 from direct contact engagement with the housing plate 40 and the end of the slat 48. Also the heat resisting spacers 80 and 81 hold the switch blade 15 in spaced relation to the sealing strips 66 and 67. The other end of the slat 48 is held by the respective spring 51 against the bottom of the groove 50 in the plate 40. The edges 78 and 79 of the resilient sealing strips 66 and 67 are in juxtaposition except where the switch blade 15 extends therebetween.

When the switch blade 15 is pivoted toward the switch open position under load, an arc is drawn between it and the stationary contact assembly 25 which impinges upon the sides of the slot 35 or the inner side of the plates 40 and 41 as well as along the surface of the slat 48. An arc extinguishing medium is evolved from these surfaces due to the heat of the are which assists in deionizing and extinguishing it accompanied, however, by the generation of high temperature gases and are particles which tend to create flashover conditions unless they are disposed of satisfactorily. As the switch blade moves past the slat 48 and between the edges 78 and 79 of the sealing strips 66 and 67 the space between it and the contact assembly 25 is closed off first by the portion of the slat 48 previously engaged by the switch blade 15 being returned to the bottom of the groove 50 and then gradually entirely into the groove 50 when the distal end of the switch blade 15 parts contact with it. Due to the flexibility of the sealing strips 66 and 67 and the contour of the switch blade 15 a substantially gas tight seal is maintained along the entrance 38 to the groove 35. The gas and arc products thus produced flow into the gas expansion chamber 61 where the gas pressure is materially reduced and thence into the muffler 88 where the pellets 101 cool, condense and deionize the are products. As a result the gas which is discharged through the perforations 90 in the outer plate 89 is free of metallic particles, is non-conducting and is at a relatively low temperature insufficient to create flashover either phase to phase, phase to ground or to the switch blade 15. Due to the pressure of the gas in the expansion chamber, the flexible sealing strips are urged thereby into sealing engagement with the juxtaposed surface of the switch blade 15.

What is claimed as new is:

1. A circuit interrupter comprising: terminals for connecting said interrupter in a circuit, contact means mounted on one of said terminals, a switch blade pivotably mounted on the other of said terminals, an insulating housing enclosing said contact means and having a slot through which said switch blade is movable into and out of engagement with said contact means, and sealing means extending along the entrance to said slot forsealing off said slot when said switch blade is pivoted from engagement with said contact means to the switch open position, said sealing means comprising a pair of flexible resilient strips each anchored along one of its edges to said housing along the entrance edges of said slot with the other edges of said strips juxtaposed to receive therebetween said switch blade to be displaced from and to scaling position by movement of said switch blade therepast, said flexible resilient strips forming a V-shaped configuration with the apex in said slot whereby pressure of gas incident to an are between said contact means and said switch blade reacts against the outer sides of said configuration and urges said strips into sealing engagement with each other and with said switch blade.

2. The circuit interrupter according to claim 1 wherein said flexible resilient strips are formed of polysulfone.

3. A circuit interrupter comprising: terminals for connecting said interupter in a circuit, contact means mounted on one of said terminals, a switch blade pivotably mounted on the other of said terminals, an insulating housing enclosing said contact means and having a slot through which said switch blade is movable into and out of engagement with said contact means, and gas expansion chamber means extending along opposite sides of the entrance to said slot through which said switch blade is pivoted for receiving, confining and lowering the pressure of are products incident to separation of said switch blade from said contact means and the formation of an arc therebetween, said gas expansion chamber means being closed along one side by flexible sealing means through which said switch blade is movable.

4. The circuit interrupter according to claim 3 wherein said sealing means comprises at least one flexible resilient strip arranged to be displaced from and to scaling position by movement of said switch blade therepast.

5. The circuit interrupter according to claim 3 wherein said sealing means comprises a pair of flexible resilient strips each anchored along one of its edges to one edge of said gas expansion chamber means along said one side thereof with the other edges of said strips juxtaposed to receive therebetween said switch blade to be displaced from and to scaling position by movement of said switch blade therepast, said flexible resilient strips forming a generally V-shaped configuration with the apex in said gas expansion chamber means whereby the pressure in said gas expansion chamber means reacts against the outer sides of said configuration and urges said strips into sealing engagement with each other and with said switch blade.

6. A circuit interrupter comprising: terminals for connecting said interrupter in a circuit, contact means mounted on one of said terminals, a switch blade pivotably mounted on the other of said terminals, an insulating housing enclosing said contact means and having a slot through which said switch blade is movable into and out of engagement with said contact means, and muffler means communicating with said slot for cooling and condensing said are products, said muffler means including a pair of apertured spaced apart plates extending transversely of said slot, and are product cooling, condensing and deionizing means in the space between said plates.

7. The circuit interrupter according to claim 6 wherein said are product cooling, condensing and deionizing means comprises activated alumina.

8. A circuit interrupter comprising: terminals for connecting said interrupter in a circuit, contact means mounted on one of said terminals, a switch blade pivotably mounted on the other of said terminals, an insulating housing enclosing said contact means and having a slot through which said switch blade is movable into and out of engagement with said contact means, gas expansion chamber means extending along the entrance to said slot through which said switch blade is pivoted for receiving and confining arc products incident to separation of said switch blade from said contact means and the formation of an arc therebetween, and muffler means at that end of said expansion chamber means through which the distal end of said switch blade is pivoted in moving between switch closed and switch open position for cooling and condensing said are products.

9. The circuit interrupter according to claim 8 wherein said muffler means includes a pair of apertured spaced apart plates extending transversely of said expansion chamber means, and are product cooling and condensing means in the space between said plates. v

10. The circuit interrupter according to claim 9 wherein said gas expansion chamber means is formed along opposite sides of said slot and is closed along one side by flexible sealing means through which said switch blade is movable.

11. The circuit interrupter according to claim 10 wherein one of said plates includes a generally V-shaped section extending to the other of said plates and opening toward the pivot axis of said switch blade, and said sealing means comprises a pair of flexible resilient strips each anchored along one of its edges to one edge of said gas expansion chamber means along said one side thereof with the other edges of said strips juxtaposed to receive therebetween said switch blade, said strips extending through said generally V-shaped section and adjacent said other plate, one side of said slot has a slat receiving groove extending partially through said housing from said slot, between said contact means and 'said switch blade in the switch open position, and transversely of said switch blade in the switch closed position, a flatarc extinguishing slat is movable in said groove transversely of said slot toward and away from the other side of said slot and with said housing closing off the space between said contact means and said switch blade in the switch open position, and means bias said slat in said groove to a position closing off said slot, said flexible resilient strips form a generally V-shaped configuration with the apex in said gas expansion chamber whereby the pressure in said gas expansion chamber means reacts against the outer sides of said configuration and urges said strips into sealing engagement with each other and with said switch blade, 

1. A circuit interrupter comprising: terminals for connecting said interrupter in a circuit, contact means mounted on one of said terminals, a switch blade pivotably mounted on the other of said terminals, an insulating housing enclosing said contact means and having a slot through which said switch blade is movable into and out of engagement with said contact means, and sealing means extending along the entrance to said slot for sealing off said slot when said switch blade is pivoted from engagement with said contact means to the switch open position, said sealing means comprising a pair of flexible resilient strips each anchored along one of its edges to said housing along the entrance edges of said slot with the other edges of said strips juxtaposed to receive therebetween said switch blade to be displaced from and to sealing position by movement of said switch blade therepast, said flexible resilient strips forming a Vshaped configuration with the apex in said slot whereby pressure of gas incident to an arc between said contact means and said switch blade reacts against the outer sides of said configuration and urges said strips into sealing engagement with each other and with said switch blade.
 2. The circuit interrupter according to claim 1 wherein said flexible resilient strips are formed of polysulfone.
 3. A circuit interrupter comprising: terminals for connecting said interupter in a circuit, contact means mounted on one of said terminals, a switch blade pivotably mounted on the other of said terminals, an insulating housing enclosing said contact means and having a slot through which said switch blade is movable into and out of engagement with said contact means, and gas expansion chamber means extending along opposite sides of the entrance to said slot through which said switch blade is pivoted for receiving, confining and lowering the pressure of arc products incident to separation of said switch blade from saId contact means and the formation of an arc therebetween, said gas expansion chamber means being closed along one side by flexible sealing means through which said switch blade is movable.
 4. The circuit interrupter according to claim 3 wherein said sealing means comprises at least one flexible resilient strip arranged to be displaced from and to sealing position by movement of said switch blade therepast.
 5. The circuit interrupter according to claim 3 wherein said sealing means comprises a pair of flexible resilient strips each anchored along one of its edges to one edge of said gas expansion chamber means along said one side thereof with the other edges of said strips juxtaposed to receive therebetween said switch blade to be displaced from and to sealing position by movement of said switch blade therepast, said flexible resilient strips forming a generally V-shaped configuration with the apex in said gas expansion chamber means whereby the pressure in said gas expansion chamber means reacts against the outer sides of said configuration and urges said strips into sealing engagement with each other and with said switch blade.
 6. A circuit interrupter comprising: terminals for connecting said interrupter in a circuit, contact means mounted on one of said terminals, a switch blade pivotably mounted on the other of said terminals, an insulating housing enclosing said contact means and having a slot through which said switch blade is movable into and out of engagement with said contact means, and muffler means communicating with said slot for cooling and condensing said arc products, said muffler means including a pair of apertured spaced apart plates extending transversely of said slot, and arc product cooling, condensing and deionizing means in the space between said plates.
 7. The circuit interrupter according to claim 6 wherein said arc product cooling, condensing and deionizing means comprises activated alumina.
 8. A circuit interrupter comprising: terminals for connecting said interrupter in a circuit, contact means mounted on one of said terminals, a switch blade pivotably mounted on the other of said terminals, an insulating housing enclosing said contact means and having a slot through which said switch blade is movable into and out of engagement with said contact means, gas expansion chamber means extending along the entrance to said slot through which said switch blade is pivoted for receiving and confining arc products incident to separation of said switch blade from said contact means and the formation of an arc therebetween, and muffler means at that end of said expansion chamber means through which the distal end of said switch blade is pivoted in moving between switch closed and switch open position for cooling and condensing said arc products.
 9. The circuit interrupter according to claim 8 wherein said muffler means includes a pair of apertured spaced apart plates extending transversely of said expansion chamber means, and arc product cooling and condensing means in the space between said plates.
 10. The circuit interrupter according to claim 9 wherein said gas expansion chamber means is formed along opposite sides of said slot and is closed along one side by flexible sealing means through which said switch blade is movable.
 11. The circuit interrupter according to claim 10 wherein one of said plates includes a generally V-shaped section extending to the other of said plates and opening toward the pivot axis of said switch blade, and said sealing means comprises a pair of flexible resilient strips each anchored along one of its edges to one edge of said gas expansion chamber means along said one side thereof with the other edges of said strips juxtaposed to receive therebetween said switch blade, said strips extending through said generally V-shaped section and adjacent said other plate, one side of said slot has a slat receiving groove extending partially through said housing from said slot, between said contact means and said switch blade in the switch open position, and transversely of said switch blade in the switch closed position, a flat arc extinguishing slat is movable in said groove transversely of said slot toward and away from the other side of said slot and with said housing closing off the space between said contact means and said switch blade in the switch open position, and means bias said slat in said groove to a position closing off said slot, said flexible resilient strips form a generally V-shaped configuration with the apex in said gas expansion chamber whereby the pressure in said gas expansion chamber means reacts against the outer sides of said configuration and urges said strips into sealing engagement with each other and with said switch blade. 